This invention relates in general to fiber optic connectors and in particular to multi-channel fiber optic connectors for connecting more than one pair of fibers.
Optical fibers used for data transmission are made with a circular core of either glass or plastic encoated with a cladding material having a lower index of refraction than the core. When the ends of two optical fibers are connected it is important for the cores of the two fibers to be aligned to maximize the amount of light signal transmitted from the end of one fiber to the end of the other. If the two fibers are not aligned the magnitude of the light signal transmitted is reduced. As the ends of the two fibers move further away from the perfectly aligned position the magnitude of the light signal transmitted continues to decrese. Optical fibers used for data transmission frequently have cores with very small diameters typically of the order of a hundred microns. Thus, connectors for connecting single pairs of optical fibers in end-to-end relationship must be capable of aligning accurately the ends of a pair of fibers with small diameters.
Frequently, it is necessary to connect together the ends of more than one pair of optical fibers. If a single channel fiber optic connector is used to connect each pair of fibers, then a number of connectors will be necessary. To connect or disconnect the pair of fibers, it is necessary to connect and disconnect each connector which may be inconvenient. In applications where the amount of space available for the connections is limited, the use of single channel fiber optic connectors may be altogether impractical. Thus, it is desirable to provide multi-channel fiber optic connectors comparable in size to single channel connectors but which are capable of simultaneously connecting and aligning more than one pair of optical fibers.
Multi-channel fiber optic connectors, however, have much more stringent requirements for tolerances than single channel connectors. Because of space considerations, it may be desirable for multi-channel connectors to be be capable of aligning accurately two or more pairs of fibers and yet are compact so that they are comparable in size to single channel connectors. The larger the number of pairs of fibers that must be aligned, the tighter will be the tolerance for the multi-channel connector. Thus, multi-channel connectors can be difficult to manufacture and are usually expensive.
Attempts have been made to design multi-channel fiber optic connectors. In one type of multi-channel connectors one or more alignment pins are provided in one part of a connector which fit into one or more corresponding holes in the other part of the connector to align the ends of two sets of optical fibers. The use of alignment pins and complementary holes are disclosed in U.S. Pat. Nos. 3,923,371 to Dalgleish, 4,076,379 to Chouinard and 4,396,248 to Bientz et al. A form of alignment pin-complementary hole type connection for aligning the fibers is also used in U.S. Pat. No. 4,405,201 to Cefarelli et al.
In another type of multi-channel optical fiber connector the connector includes an alignment member having two surfaces inclined twoards each other in the form of a V and two oppositely situated ferrules resting on the two surfaces. The fibers and the two ferrules are then aligned by the two surfaces forming the V. This type of connection is disclosed in U.S. Pat. No. 4,258,977 to Lukas et al. UK Pat. No. 1 576 336 also employs V shaped channels in two different holders for aligning two fibers each placed in one of the holders. The V shaped channels are such that the fibers are offset relative to the axes of the holders. The two holders are then rotated relative to each other about the axes and the position of maximum light transmission from one fiber to the other is determined to align the ends of the fibers.
None of the above described multi-channel connectors are entirely satisfactory. In the type of connector utilizing an alignment pin and a complementary hole, the size of the hole must be larger than the pin so that the pin may be inserted therein. Thus, the pin may contact the hole surface at only one point allowing the pin to move about in the hole which changes the alignment of the fibers. It is thus desirable to provide a multi-channel fiber optic connector which provides better alignment capabilities, is inexpensive and which may be used to connect and disconnect a number of optical fibers repeatedly.